In a high-pressure pipe system, the immediate result of a rupture on the supply side of the system, which is connected to a pump or the like, is a considerable pressure drop leading to a reversal of fluid flow from the low-pressure side of the rupture opposite the pump. As fluid from the low-pressure side of the pipe system flows through the rupture, considerable acceleration of the fluid and a much higher mass flow than normal exists. Check valves have been used in high-pressure pipe systems which can respond to ruptures of this type by closing off and damaged pipes rapidly, thus preventing heavy losses of fluid through the rupture. That is, if a rupture occurs between a source of fluid under pressure and a check valve in the pipe system, the reduction in pressure on the inlet side of the check valve will permit it to close, thus preventing reverse flow of fluid beyond the check valve back through the rupture. As will be appreciated, the check valve should close with all possible speed in the interest of minimum leakage through the rupture; however, an over-abrupt closure causes a correspondingly abrupt deceleration of fluid flow with the resulting risk of pressure surges and shocks which may damage the undamaged piping or other pipe system items, particularly in the case where the fluid comprises a liquid.
Conventional check valves used in high-pressure pipe systems of the type described above usually employ a valve element in the shape of a disc, similar to an internal combustion valve element. The closing movement of a conventional disc-shaped valve of this type is relatively short, on the order of about one-third the diameter of the disc-valve element. As a result, the closing time is correspondingly short; and in the event of a flow reversal caused by a pipe rupture, the resulting above-normal pressure drop reduces the closing time still further. Provision must, therefore, be made for damping the closing movement of the check valve. At the same time, it is desirable to have the valve open with a minimum pressure differential between its inlet and outlet ports.